Conventional method of cold forming metal tubes to create structural members, for example, for the automotive industry, is hydroforming. In a typical hydroforming process, a metallic sheet and/or metal hollow tube is partially deformed by stamping it in a hydroforming die element. Then, internal hydraulic pressure exceeding the yield strength of the tube wall is applied to force the tube to expand and conform to the die cavity.
After either the hydroforming process or the liquid impact forming process, holes are typically pierced or punched into the structural tube, for example, to provide points of attachment. Typically, punching holes deforms the metal surrounding the hole.
U.S. Pat. No. 7,552,535 relates to a method for manufacturing a hydroforming member includes the step of providing a blank. The blank is defined by blank wall. The blank is placed in a die assembly having a die cavity defined by a die surface. The blank is expanded so that the blank wall is forced against the die surface to form the hydroformed member. A portion of the blank wall conforms against a wall-thinning element positioned along the die surface to form a removable wall section in a portion of the blank wall. The removable wall section is then removed from the blank wall to form an opening in the hydroformed member in a separate die and process.